NCT01387347 tested RGN-259, a finished ophthalmic formulation containing full-length thymosin beta-4, against its vehicle in 72 adults with dry eye. Neither registered day29 primary comparison showed statistically significant benefit. Some analyses of other eye regions or time points favored RGN-259, but they do not turn the two negative primary results into a successful trial.[1][2]
This record separates those findings from uncertain missing-data handling, inconsistent safety reporting and the identity of the tested material. Full-length, 43-amino-acid thymosin beta-4 is not the seven-amino-acid fragment described as TB-500 in the FDA briefing used here. Neither a shared name nor a favorable secondary result validates another formulation or supplier's material.[1][3]
Study at a glance
| Field | What was studied |
|---|---|
| Design | Randomized, vehicle-controlled phase2 trial at one center; paper describes double masking, current registry classifies four masked roles |
| Participants | 72 adults with dry-eye signs and symptoms, 36 per group |
| Selection | Eligibility included dry-eye history and qualifying responses to a controlled adverse environment challenge |
| Test article | RGN-259: preservative-free sterile ophthalmic solution containing 0.1% w/w synthetic full-length thymosin beta-4 |
| Comparator | Matching vehicle with the same excipients but without thymosin beta-4 |
| Main assessment | Day29/visit5, after the day28 controlled adverse environment challenge |
| Co-primary outcomes | Inferior corneal fluorescein staining and ocular discomfort in one designated worst eye |
| Identifiers | NCT01387347; protocol RGN-DE-202; PMID26056426; DOI10.2147/OPTH.S80954 |
| Current registry | Completed, actual enrollment72; last update posted July10,2015, read for this review in September2026 |
The controlled adverse environment, or CAE, deliberately challenges the ocular surface under standardized conditions. A response in this selected population and setting does not automatically describe ordinary daily symptoms or longer-term dry-eye experience.[1][2]
Efficacy was assessed in one designated eye per participant; this is not a trial of 144 independent eyes. The worst-eye selection used staining change, then discomfort and a specified tie-breaker. Safety assessments could involve both eyes. Formulation details identify the experiment; they are not preparation or treatment instructions.[1][2]
Both registered primary outcomes were negative
Both scales ran from0 to4, with higher scores worse. The registry labels each primary analysis intention-to-treat with36 participants per arm. Its posted two-sided, unequal-variance t-tests compare day29 final scores.[2]
| Day29 primary outcome | RGN-259 mean | Vehicle mean | Active minus vehicle | Registry t-test P |
|---|---|---|---|---|
| Inferior corneal staining | 2.08 | 1.90 | +0.18 | .2596 |
| Ocular discomfort | 1.6 | 1.3 | +0.3 | .3734 |
The observed mean directions did not favor lower scores with RGN-259. However, a nonsignificant comparison is not proof of equal effects, equivalent safety or absence of every potentially important benefit or harm. The displayed registry analyses do not supply a between-group confidence interval.[2] See what a negative or null result means.
The publication also reports Wilcoxon P=.2586 for staining and P=.2210 for discomfort. Its ANCOVA results give adjusted differences of+0.14, P=.3452, and+0.2, P=.4901, respectively. Those analyses are also negative, but their P values should not be substituted for the registered t-tests.[1]
The methods describe unequal-variance t-tests as the primary comparison and Wilcoxon tests as sensitivity analyses. There is also a reporting inconsistency: the methods name visit1 pre-CAE as the ANCOVA baseline, while the results describe a visit2 covariate. This review does not resolve that difference or certify one common adjusted model.[1]
Selected secondary findings are different questions
The paper examined several regions, visits and analysis methods, including additional analyses described as ad hoc. An original dated statistical analysis plan and complete amendment history were not obtained for this review, so the prospective status and overall multiplicity control of every positive comparison cannot be certified.[1]
Three examples show why the exact question matters:
- Central staining: Table3 reports change from visit2 to visit5 of−0.36 with RGN-259 and+0.16 with vehicle, with t-test P=.0075 and Wilcoxon P=.0066. The narrative gives−0.37 for the active change; that small source discrepancy is not silently repaired.
- Superior staining: a narrative/figure comparison reports P=.0210. Table3 also presents a superior-region comparison with t-test P=.0109 and Wilcoxon P=.0181. These should not be presented as interchangeable values for one verified contrast.
- Discomfort during the day28 challenge: the abstract/figure and registry additional analysis report P=.0244; nearby paper prose gives P=.0224. Neither is the day29 primary discomfort comparison.[1][2]
A peripheral-staining comparison further illustrates sensitivity to method: t-test P=.0379 versus Wilcoxon P=.0741. Favorable results among multiple regions and time points warrant follow-up, not a broad conclusion that the treatment was effective.[1]
The current registry's only listed secondary outcome measure is an adverse-event measure; selected regional and day28 efficacy analyses appear as additional analyses under the primary result entries. Publication labels and registry organization are not identical evidence that every analysis was prospectively planned. See confidence intervals, P values and multiplicity.[2]
Completion, intention-to-treat and missing outcomes
| Population or flow item | RGN-259 | Vehicle |
|---|---|---|
| Randomized / registry Overall Study started | 36 | 36 |
| Completed, registry Overall Study period | 35 | 34 |
| Not completed, classified as lost to follow-up in registry | 1 | 2 |
| Listed in each registered primary analysis | 36 | 36 |
The 69-person completion total does not establish that all72 contributed observed measurements at every visit. A table labeled intention-to-treat with36 per arm is not itself an explanation of how missing outcomes were handled.[1][2]
The paper reports five major protocol deviations excluded from the per-protocol analysis. The reviewed text does not establish their arm distribution, overlap with noncompletion or a complete missing-data rule. They must not simply be subtracted again from the69 completers, and a restricted analysis cannot automatically replace the randomized comparison.[1]
The registry's Overall Study completion label is retained as written, rather than converted into a separately verified four-week completion endpoint. Its recruitment narrative and top-level completion dates also differ; this review does not infer a reconciled timeline.[2] Related guides explain intention-to-treat and per-protocol sets and trial estimands and missing data.
Adverse-event reporting needs more than the abstract
The publication abstract's broad no-event wording does not match its detailed results. The latter report at least one ocular treatment-emergent adverse event in2/36 active participants and5/36 vehicle participants. The paper defines treatment-emergent events as new or worsened after first exposure through visit6. Ocular event categories can overlap within a person and should not be summed into another participant total.[1]
The detailed results also describe one withdrawal after moderately severe vomiting judged unrelated by investigators. The exposed paragraph does not identify the participant's arm. This withdrawal description is not reconciled with the registry's classification of all three noncompletions as lost to follow-up. An investigator's unrelatedness assessment does not erase the event or establish its cause independently.[1][2]
The registry contains two different safety summaries:
- Its secondary outcome table reports2 vehicle versus0 active events through day29, under a measure described using visual acuity, intraocular pressure and corneal sensitivity.
- Its separate nonserious-event module reports instillation-site pain affecting2/36 vehicle versus0/36 active participants, with four events in those two vehicle participants. The reporting threshold is2%, assessment is described as non-systematic, and that module's timeframe is unspecified.[2]
Those are different reporting objects, not interchangeable counts. The module records no serious adverse events in either36-person group, but its mortality totals are blank rather than verified zeros. Neither absence of a reported serious event nor the small numerical imbalance proves safety equivalence or excludes uncommon or delayed harm.[2]
Sponsor and disclosure context
The current registry identifies ReGenTree LLC as sponsor/responsible party and Ora Inc as collaborator. The publication includes an Ora-affiliated author and declares no conflicts of interest. A separate stand-alone funding statement was not verified in the indexed text reviewed here.[1][2]
The registry also reports an agreement restricting investigators' discussion or publication after study completion; the detailed terms are not supplied. That is distinct from the declaration that investigators were not sponsor employees. Sponsorship, product attribution, employment, conflicts declarations and publication rights should not be collapsed into a claim of fully independent conduct or an allegation of undisclosed wrongdoing.[2]
Full-length thymosin beta-4 is not the TB-500 fragment
RGN-259 was a defined formulation of full-length, 43-amino-acid thymosin beta-4. The FDA memorandum dated May15,2026, prepared for the July23–24 Pharmacy Compounding Advisory Committee meeting, describes TB-500 free base as an N-terminally acetylated seven-amino-acid fragment corresponding to residues17–23. It also distinguishes salts and other chemical entities and warns that commercial use of the common name can be inconsistent.[1][3]
That briefing concerns a wound-healing compounding assessment, not validation of this dry-eye trial. Its cover explicitly identifies advisory background preceding a final determination. This page does not treat it as a new current approval check or final legal ruling.[3]
Neither the trial nor the briefing authenticates another product's sequence, modification, purity, sterility, stability, formulation or clinical effect. Evidence cannot be transferred merely because a label uses “thymosin beta-4” or “TB-500.” See approved drugs versus research materials.
What the evidence supports, and what remains uncertain
The strongest trial-level conclusion is that neither registered primary comparison showed superiority. The selected secondary findings can inform future questions, but they do not establish consistent improvement in signs and symptoms, durable benefit or superiority to established dry-eye care.[1][2]
Important limitations include the small single-center sample, challenge-based selection, brief follow-up, multiple analyses, incomplete verification of missing-data handling and differences between paper and registry reporting. Staining is an ocular sign and discomfort is a symptom; statistical significance at one location or time does not establish clinically meaningful benefit across the disease experience.
Frequently asked questions
Did either primary endpoint succeed?
No. Both day29 registered t-tests were nonsignificant. The publication's reported Wilcoxon and ANCOVA primary results were also nonsignificant.
Why are several different P values reported?
They belong to different methods, regions or time-point comparisons. Keep the test and endpoint attached to each value; a favorable day28 or regional result cannot replace a negative day29 primary result.
Do the positive secondary findings show that RGN-259 works?
They identify signals worth studying, not a confirmed overall benefit. Multiple comparisons, ad hoc analyses and unverified original analysis-plan details limit that inference.
Were there really no adverse events?
No. Detailed paper results and registry tables report events, although their definitions and totals differ. One vomiting-related withdrawal is described, without a verified arm assignment in the reviewed paragraph.
Did all72 participants complete every assessment?
No. The registry lists69 completers. Its36-per-arm primary analysis labels do not establish complete observed data or explain missing-outcome handling; five per-protocol exclusions are another, not necessarily separate, group.
Is the tested material the same as TB-500?
The trial used full-length43-amino-acid thymosin beta-4. The FDA identity discussion describes an acetylated seven-amino-acid fragment, and warns that TB-500 naming is inconsistent. A name alone cannot establish equivalence.
Does this record justify treating dry eye with another peptide product?
No. It neither provides treatment instructions nor establishes another product's identity, quality, safety or benefit. The randomized primary comparisons were negative.
Related research guides
Continue with how to read a research study, return to the Study Library, or browse the Research Library.
Sources and review limits
- Sosne and Ousler primary article: PMC4445951, indexed official text reviewed
- ClinicalTrials.gov: NCT01387347, current study details and posted results
- FDA 2026 TB-500 briefing, dated identity and advisory-context sections
- PubMed identifier: PMID26056426
- Publication DOI: 10.2147/OPTH.S80954
Editorial evidence review: September 3, 2026. This is an editorial critical summary, not an independent specialist review. Direct article/metadata access encountered challenges; ordinarily indexed official article sections, current registry details/results and selected FDA text and identity-page images were reviewed. A complete fresh primary-paper PDF, its table/figure images, original protocol/SAP, full history, participant data and exhaustive correction/retraction check were not obtained. The DOI is an identifier, not a claim of fresh publisher full-text review. No current product-approval determination is made. Contact us about corrections.